Biosafety in the laboratory - VIB

The effectiveness of different decontaminants
Fungi bacteria mycobacteria spores lipid non-lipid
viruses viruses
Ethanol - +++ +++ - + V
Hypochlorite + +++ ++ ++ + +
Formaldehyde +++ +++ +++ +++* + +
Peroxide + +++ ++ ++ + +
* above 40 °C V = variable
Inactivation
It is often quite difficult to destroy biological material. Bacterial spores, for instance, are
resistant to temperatures of 100°C. Sterilisation - heating water under pressure at a temperature
of 121°C for 20 minutes - is the recommended method in such cases. Sometimes
the water is even heated at temperatures of 134°C. This is a very effective way to inactivate
micro-organisms, provided that the steam can reach all areas in need of sterilisation. Air
pockets are a well-known problem. Even animal cells are known to be able to survive in
an air pocket during the sterilisation process. A sterilisation tank should be filled in a very
careful manner, and all caps should be loosened. Sterilisation is the recommended method
to kill bacteria, yeasts, and fungi. For other organisms, like plant and animal cells, and
some viruses, simpler methods are available. Heating up to 80°C or exposing the cells to
strong detergents is often sufficient to kill them. It is, however, highly important to check
whether the method to be used is a validated one; in other words, whether the organisms
will be effectively destroyed. Inactivation is much more effective in killing micro-organisms
than superficial decontamination: if well-performed, inactivation can be 100 % effective.
When bacteria present in fluids need to be killed, sodium hypochlorite solutions are often
used. It is important to make sure that the final level of chlorine in such solutions is high
enough to kill the bacteria (20-100ml/l). It should be mentioned that sterilisation is still
the most environmentally friendly method. In practice, the fluids containing chlorine are
poured down the drain all too often. Principly, fluids containing substances that might
affect the proper functioning of a water purification plant should not end up in the company’s
waste water. For a decontaminant to be effective, it is also very important that it is
in contact with the micro-organisms long enough, i.e. for at least 15 to 30 minutes in
general.
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Biosafety in the laboratory